In recent years, optical hub sites such as an optical add-drop multiplexer (OADM) and a wavelength cross connect (WXC) have been developed in the optical network field. The OADM adds and drops an optical signal on a wavelength basis. The WXC switches a path of an optical signal on a wavelength basis. The optical hub sites allow an optical network with a complex topology such as mutually coupled links or a mesh structure to be built. The sizes of networks have increased.
As a conventional technique, an optical network designing method has been proposed, which is to reliably calculate a currently used optical path and an auxiliary optical path at a high speed in an optical network in which a plurality of optical transfer links share a single optical transfer device so that the network cost is minimized (for example, refer to Japanese Unexamined Patent Application Publication No. 2006-67067).
As another conventional technique, an optical network designing method has been proposed, which is to design an optical network that is tolerant of a variation in traffic (for example, refer to Japanese Unexamined Patent Application Publication No. 2005-86675).